Originally posted by JOlive
The best firmware out now is probably 4.50 ITA DEX CFW, it allows you to go online by just opening a homebrew app and pressing a few things.
What you need to do is downgrade to 3.55 DEX, then upgrade to 4.50 ITA, it is pretty easy to do.
When you are on ITA, run ITA manager go to network tools and restore original console id, then you can sign in. There is a few tutorials around NGU if you have a look.
Concerning PS2 backups, you'll have to research yourself unless someone else posts a reply about them, I haven't a clue.